Mycosphaerellales » Mycosphaerellaceae


Pseudocercosporidium Deighton, Mycol. Pap. 133: 55 (1973).

Index Fungorum number: IF 9561; Facesoffungi number: FoF 08643, 1 morphological species (Species Fungorum 2022), no molecular data available.

Caespituli hypophyllous, more or less effuse, often confluent, green or grey-green, subvelutinous, irregularly distributed over the whole leaf surface. Mycelium internal: hyphae nearly colorless, branched, septate. Stroma absent. Solitary hyphae or a group of a few hyphae penetrate a stoma and develop into conidiophores.  Conidiophores laxly erect, faintly green-tinged, loosely branched, thin-walled, smooth, septate, often swollen towards the apex when numerous conidial scars are there aggregated and more wide. The conidiophore apex, after the conidium has been shed, is truncate-conoid and strongly thickened and refractive, at the base of the thickened area. The central pore can be seen a very minute ‘frill’.  This is where the outer wall of the conidium was adherent to the conidiophore and matches in width with the truncate hilum of the conidium. The old scar is afterwards displaced to one side and is then visible as a highly refractive colorless thickened prominence with the base more or less flat against the side of the conidiophore. Conidia initially smoky, generally rapidly becoming deep olivaceous, at first oblong-ellipsoid, occasionally subcylindric and 1–septate, later obclavate and 3–6 septate, largely obtuse at the apex with a truncate unthickened hilum, smooth, thin-walled, straight or slightly curved not constricted or occasionally somewhat constricted at some of the septa. Some shorter 1–2 septate conidia are deeply colored while some longer obclavate 3–5 septate conidia may remain relatively pale. Most conidia are 3 septate (adapted from Deighton 1973).


Type species: Pseudocercosporidium venezuelanum (Syd.) Deighton


Notes: Pseudocercosporidium resembles Passalora, but is distinct in the structure of the conidiogenous loci that are not thickened or darkened (Braun 2013). Pseudocercosporidium lacks sequence data. The placement of Pseudocercosporidium in Mycosphaerellaceae is doubtful.


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